Today I have purchased some $\ce{HCl(aq)}$ on my local market with a concentration of 23%.
However, I need to obtain a concentration of 37% in order to perform an experiment. Can I use distillation process to increase the acid concentration?
If yes, can I use standard chemistry glassware to process it? (In an isolated system to prevent the $\ce{HCl(g)}$ from escaping of course.)

Distillation unit

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    $\begingroup$ If that experience is you feeling a lot of pain, this would do it. Depending on how much acid you have casually bought, this could be really dangerous. HCl is a gas, if you heat up your little experiment, it will go wherever it pleases, most likely heavily react with your body, you will also breathe it in and it could get into your eyes, making you blind and helpless. Please stop whatever you are doing before people get hurt. $\endgroup$ – AMT Mar 3 '17 at 11:08
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    $\begingroup$ Why not adjust the other reactants in your reaction in order to reach the same concentrations throughout the process? This seems a lot safer. Would you mind sharing with us your procedure? $\endgroup$ – Felipe S. S. Schneider Mar 3 '17 at 12:12
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    $\begingroup$ What experiment are you attempting? 23% HCl strikes me as concentrated enough to do most reactions that call for conc. HCl. $\endgroup$ – Waylander Mar 3 '17 at 12:24
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    $\begingroup$ As sternly warned by users above, there are serious safety issues at play here, so please do your due diligence about precautions and consult an expert if need be. $\endgroup$ – jonsca Mar 4 '17 at 1:43
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    $\begingroup$ you mention using an isolated system, closed glassware apparatuses are seriously dangerous when performing chemical reactions! Your usually heating up something, or the reaction might produce gas by itself. This means your apparatus has to withstand the significant pressure this causes, and it won't do that. The result will be that you're picking out the glass shrapnel from your face while you're lungs are burned by the gaseous HCl you set free. There is no way to perform this reaction safely without a fume hood and expertise. $\endgroup$ – Mad Scientist Mar 4 '17 at 12:23

Add Calcium Chloride to destroy the azeotrope. Then distill and capture the vapor phase.

See the second method "Extractive Distillation" here:


(Obviously, proper equipment and safety precautions are essential.)


Irrespective of the potential hazards to an inexperienced chemist attempting distillation of hydrochloric acid, especially absence of adequate safety measures such as a fume hood, in this case, distillation will not result in a higher concentration of acid. Hydrogen chloride and water form a constant-boiling mixture (azeotrope) at ~20% HCl, which is what you are already starting with. I suggest you read the Wikipedia page on Hydrochloric Acid for starters.


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